Engines operating on gaseous fuels, such as natural gas, are commonly supplied with a lean fuel mixture, which is a mixture of air and fuel containing a relatively high ratio of air to fuel. The lean fuel mixture often results in misfires, detonation, incomplete combustion and poor fuel economy. One factor that can lead to such events is the poor ability of conventional spark plugs to effectively ignite a lean fuel mixture in the cylinder of the operating engine. More effective combustion of lean fuel mixtures can be achieved using a pre-combustion chamber.
Pre-chamber (i.e., pre-combustion chamber) spark plugs are typically used to enhance the flammability limits in engines such as natural gas burn engines. As in any spark plug, the pre-chamber spark plugs typically include a pair of electrodes including a ground electrode and a charged electrode. The ground electrode is annular shaped with the a plurality of radially inward projecting tips that surround the charged electrode. Consequently, the charged electrode generally extends axially into the charged electrode generally along a central axis defined by the annular ground electrode.
To extend spark plug life, the tips generally include a precious metal (PM) material secured to a base material. Unfortunately, in the past, individual pieces of the PM material was laser welded onto the base material of each tip. This requires expensive tooling and product specific fixturing equipment to hold the individual pieces of PM material during the laser welding process. Due to the complexity of the ground electrode geometry, the manufacturing of the pre-chamber spark plug tends to be a tedious, time consuming, and expensive process. Further, due to the potential for error or improper manufacturing due to the need to fixture the individual pieces of PM material to the base material portion of the tips, the prior processes result in less reliable or robust ground electrodes.
There is a need, therefore, for improvements in methods of manufacturing pre-chamber spark plugs and particularly ground electrodes for pre-chamber spark plugs that overcome one or more of the above identified problems existing in the art. Embodiments of the present invention provide such improved methods.